for surveillance and geo-location

Presented by: Giuseppe Savoia

RF Sensor Networks

October 2010

Creating Sensor Networks with the N6841A

S800 Module 305

RF Sensor Networks Overview

October 2010

• Why RF Sensors

• Key Capabilities and Applications

• RF Sensor main features

• Monitoring & Analysis Software

• Emitter Geolocation Software

• Summary

Page 2

Creating Sensor Networks with the N6841A

S800 Module 305

Why RF Sensors? - Trends in RF Technology

Page 3

Our Customer’s Challenge:

Quickly detect and locate non-cooperative modern signals which

may be intermittent, be of short duration, spread spectrum, have

low power and/or low energy.

Frequencies and

Bandwidths

Increasing

Signal

Complexity

Increasing

Number of

Transmitters

Increasing

Lower

Transmiter Power

October 2010

Creating Sensor Networks with the N6841A

S800 Module 305

RF trends drive need for RF Sensors

& Sensor Networks

Networked Sensors• Transfer data to common processing

point for processing gain

• Distributed (redundant) measurements

• Application platform for new capabilities

Synchronization• Required because of dynamic signal

environment

• Required for geolocation

Quantity of Sensors• Trade off density with price/performance

of individual receivers

• Proximity to target provides gain

Page 4

Network

N6854A

Geolocation

Server s/w

N6820E Surveyor

N6841A

October 2010

Potentially better at detecting and locating modern signals

• Lower power/energy, higher bandwidths, higher frequencies

• More complicated modulations schemes

• Multiple synchronized spatially-separated views of same signal

Takes advantage of advances in networking

• Capacity, Speed, Accessibility

• Optical, Wired, Wireless

Configurable

• New tasks, New requirements, New signals

• Multi-tasking (part of a sensor network is doing something different)

• Expandable (new sensors), Dynamic (sensors can move)

• Robust (system still works if part of the sensor network goes off-line).

• Integrate and complement existing monitoring assets

Ease of installation

• Large directional antennas not required

• Broad frequency range with inexpensive antenna

• Smaller footprint – proximity to emitters

RF Sensor Network Value Points

October 2010

Detection Probability varies with Signal Frequency

& Bandwidth

400 MHz

20 kHz

3 GHz

20 kHz

3 GHz

20 MHz

Frequency:

Bandwidth:

Noise Power Increases,

Signal PSD Decreases with

Bandwidth

Path Loss Increases

with Frequency

3 km

October 2010

Coherent vs. Non-coherent Detection

Probability of Signal Detection: Blue > 80% Red < 30%

Synchronized Receivers using

Coherent Detection

Traditional Monitoring Stations

using Non-Coherent Detection

1.6 GHz, 200 kHz BW, 300mW

Performance of

System is Limited

to performance of

receivers

System

Performance

Exceeds Receiver

Performance

October 2010

Creating Sensor Networks with the N6841A

S800 Module 305

Coherent Signal Detection using Cross-Correlations

A GSM signal is visible in

the sensor 5 spectrum,

but not in the spectrums

for sensors 2 and 4.

Even without a visible

signal in the spectrums

for sensors 2 and 4, the

cross-correlation between

data from these two

sensors produces a clear

correlation peak.

With the GSM signal

clearly visible in the

spectrum for sensor 5, it’s

expected that the sensor

2-5 cross correlation

would have a stronger

peak.

Spectrum 5

Spectrum 2

Spectrum 4

xCorr 2-5

xCorr 2-4

With two usable cross-correlations, this signal can be located

October 2010

Creating Sensor Networks with the N6841A

S800 Module 305

Proximity GainP

ow

er

Distance

20log(d)

35log(d)

50log(d)

Signal Strength Increases with Decreasing DistanceIn urban environments

proximity gain might

typically provide 10dB of

gain for a 50% reduction

in distance

Proximity

Gain

Free-space

Dense Urban

October 2010

Benefits of Precise

Measurement

Synchronization

• Time-selectivity in crowded

signal environments (e.g. TDD,

FHSS, Shared Spectrum)

• Better comparative

measurements of power and

spectral shapes on modulated

and dynamic waveforms

• Processing gain for better

sensitivity (coherent detection).

• Geolocation of emitters

Receiver 1

Receiver 2

Without accurate time

synchronization, the following

questions cannot be answered:

1. Are the RX1 and RX2

spectrums from the same

transmitter?

2. If so, is the transmitter

signal stronger at RX1, or

did the TX power change

over time?

3. Is transmitter energy

reaching Receiver 3?

4. Where is the transmitter

located?

Receiver 3

October 2010

Sensor Network Deployment Considerations

Measurement Environment

• Outdoor rural, urban or indoor

Sensor Density & Geometry

• Number of sensors –site options

• Accuracy Requirements

• Detection of weak signals

• Multi-path

Sensor receiver & antenna specifications

• Performance versus quantity tradeoff

System time coherency

• Nanoseconds of timing jitter for best accuracy

Network backhaul

• Available bandwidth

• Traffic & network management

October 2010

Agilent’s New N6841A RF Sensor

New low cost RF front-end

For signal intercept, monitoring,

geolocation

New outdoor deployable digital receiver

For systems integrators and end-users

Expand reach into new applications

Provides new deployment options

Remote receiver with open application

interface and gapless IQ and/or power

spectrum data streaming

A distributed RF measurement platform

For software-defined networked

applications:

Emitter geolocation

Coherent signal detection

Signal of interest identification

LANRF Inputs

1 & 2

DC

PowerGPS

Size: 292 x 220 x 50 mm

October 2010

October 2010

N6841A RF Features

• 20 to 6000 MHz coverage

• 3rd party up/down converters available

• 20 MHz information bandwidth

• Co-location of receiver with antenna minimizes RF coax

length and signal loss

• 2 RF inputs for multiple antennas

• Software auto-selects port based on frequency (user specified)

• Front end pre-selection filters

Time Synchronization Methods

• External reference 1 PPS sync’s N6841A internal clock

• Timestamp of data includes calibration of sensor

internal time delay

1. Optional GPS module

• Optimized GPS module for time sync applications

(~ 20 nsec jitter)

2. Network based Precision Time Protocol based on IEEE

1588-2008 standard

• Integrated in hardware in N6841A RF Sensors

• Provides alternate method of synchronization when

GPS can’t be used• Indoor Environments; GPS frequency monitoring; GPS

jamming

• Time accuracies similar to GPS (10’s of nsec or

better)

• PTP-compatible switches now available from several

networking vendors• Cisco, Hirschmann, Symetricon, Ruggedcom, On-Time

Networks, etc.

• Core technology for PTP was originally invented by

HP/Agilent

1588 Switch

MasterClock

(or RF sensor as Master)

GPS internal

module with

external antenna

October 2010

RF Sensor Placement Optimization Tool

October 2010

• Simulation & planning tool to

evaluate system performance and

sensitivity of a given sensor

deployment scenario

• Included with RF sensor

software

• User input variables:

•Sensors and locations

•Antenna characteristics

•Propagation & terrain model

•Transmitter characteristics

• Outputs:

•Signal Detection coverage &

sensitivity

•Geolocation sensitivity &

accuracy (for N6854A

software)

N6854A RF Geolocation Server

• Software that provides location of non-

cooperative RF emitters

• Employs a network of time synchronized

N6841A RF Sensors

• Multiple geolocation methods available

• Operated manually or controlled from external

application (N6820E, customer application)

• Returns predicted lat/long (EP), Circular Error

Probable (CEP), measurement quality

tentagram display

Geolocation

Display

Network

N6854A

Geolocation

Server S/W

N6820E Surveyor

Page 16 October 2010

The Tentagram Geolocation Display

October 2010

• Measurement information superimposed on area map

• Color scheme illustrates degree of signal cross-correlation as

function of location

• Provides qualitative insight into signal environment

• Highlights multipath effects, co-channel transmitters

• Likelihood map

Degree of signal

correlation

Emitter estimate of

position (EP)

Geolocation Methods Available

• Time Difference of Arrival

• Measure Time of arrival of signal feature at 3 or more sensors

• Time difference between sensors forms hyperbolic of position

• Intersection of hyperbolic is EP

• Relative Signal Strength Amplitude Ratio

• Compares signal strength at 4 or more sensors

• Amplitude ratio between sensors forms circle of position

• Intersection of circles is EP

• Hybrid

• Combines both techniques in an adaptive approach

• Different weighting of variables depending on measurement environment

October 2010

TDOA with 3 Receivers

3rd receiver enables an estimated position (EP) or “fix” of the transmitter to be calculated

Adding additional receivers allows for redundancy

R1

R3

R2

October 2010

Effect of Signal Bandwidth

1 MHz BW

100 kHz

10 kHz

• Wider signal bandwidth results in

narrower tentagram and lower CEP

October 2010

Corresponding Cross Correlations

Varying signal BW

1 MHz BW

100 kHz

10 kHz

October 2010

TDOA with remote emitters

October 2010

• Using only 2 sensors for measurement returns a hyperbolic

of position (HOP)

• Combine 2 different measurement pairs determines estimate

of position

• 3rd pair resolves ambiguity for fix of location

Emitter EP

Sensors

HOP

Relative Signal Strength Geolocation Method

October 2010

• Signal strength decreases as function of

distance in predictable manner

• typically ~1/r2 to 1/r4

• Ratio of signal amplitudes between two

sensors forms circle of position

• Intersection of multiple circles provides

EP

• Need 4 sensors to resolve all ambiguity

• Agilent A-RSS method employs proprietary

algorithm based on signal cross-correlation

• Low sensitivity to timing jitter

• Requires more SNR than TDOA method

• Sensitive to antenna & cable characteristics

Hybrid Geolocation Method

• Adaptive technique that combines A-TDOA and A-RSS

algorithms

• Input parameters include signal power, measurement

bandwidth and sensor spacing

• Weighs algorithms using proprietary technique for optimum

results

October 2010

Indoor Geolocation

• A-RSS or A-Hybrid algorithms are well suited for indoor geolocation

800 MHz wireless

microphone

October 2010

Geolocation Technique application

October 2010

All measurement results can be recomputed using alternative method

Creating Sensor Networks with the N6841A

S800 Module 305

Geolocation Visualization Tools

Software includes utility

to export geolocation

results in KML format

October 2010

October 2010

Summary

1. N6841A and N6854A is a new deployment model for signal monitoring.

• Proximity monitoring

• Need to get close to target emitters 24/7 for improved probability of detection and geolocation accuracy.

2. Redundancy in measurements improves both detection ability and geolocation accuracy.

• Sensor networks can be employed in multi-path and weak signal environments.

• Emitters can be geolocated in many cases with a negative SNR (ie below the noise floor).

• Use alternate geolcation methods depending on deployment environment.

3. Deployment planning is essential.

• Sensor density (& placement) geometry

• System time coherency

Creating Sensor Networks with the N6841A

S800 Module 305

Q & A

October 2010